Question

How do I check whether a string fits this format:

<number>,<number>,<number>

e.g.

3.0, 87546,0.8273456

i.e. three comma-separated values that can be parsed as doubles. Sometimes the string will contain something else (e.g. Text,More text,42 or anything, really) and in such a case I just need to ignore it and move on to parsing the next string.

Right now I just try to parse the string as if it fits the expected format, and catch any resulting exception. What is a smarter and less expensive way of doing this? Hopefully without throwing/catching exceptions?

        String[] parsedLine = line.trim().split(",");
        if (parsedLine.length == 3) {
            try {
                xCoordinate = Double.parseDouble(parsedLine[0]);
                yCoordinate = Double.parseDouble(parsedLine[1]);
                groundElevation = Double.parseDouble(parsedLine[2]);
            } catch (NumberFormatException nfe) {
                //This line does not contain numbers exclusively. 
                //Assume it's a header/comment.
                //Do nothing.
            }
        } else {
            //This is not in the expected x,y,z format. 
            //Assume it's a header/comment.
            //Do nothing.
        }

Answer 1

What you have right now is probably the most bullet-proof (and in my view the easiest to understand) implementation possible.

I wouldn’t change it, unless I had specific evidence from the profiler that it’s an overall bottleneck (either in terms of CPU usage, or the amount of garbage created).